"I want the world to see what I can see. To feel what I can feel. Freedom from the boundaries of the physical reality. That was the purpose of developing the REV." - J.F.
REV: Reverse Energy Vectors
Dr. Fung propelling instructor Quoc with two fingers only, based on elementary REV principles. See below "Basic Principles of REV" for explanations.
Traditionally, Tai Chi teachings are based on a system of ancient Chinese mathematics, physics, and metaphysics. It is a very good way to express the internal dynamics, but unfortunately people nowadays who are trained in western science and in western mathematics find the traditional Chinese model of the universe very esoteric and very hard to understand. Furthermore, Newtonian physics does play a very important role in the generation of physical power, and Chinese physics does not address the interaction of forces very clearly.
Basically, laws of the universe are always the same, whether expressed in the East or in the West. By integrating Eastern and Western sciences and philosophies together, Dr. Fung had developed the REV (Reverse Energy Vector) System based on traditional teachings of Yang Jian Hou and the Tai Chi Classics. The aim of REV is to express the most intricate internal dynamics of Tai Chi in such a way that everyone could understand and benefit. Although some of the ideas do seem rather strange and improbable initially, by letting go of your physical logic, believing in this Tai Chi anyone can readily experience the internal power. You no longer have to be a scholar of ancient China to understand the inner most secrets of Tai Chi internal power!
Tai Chi Power as explained in Newtonian Physics
Newton's equation on Kinetic energy: K=1/2 m V^2
where K=kinetic energy, m=mass, and V=velocity
in Tai Chi, the equation can be arranged as V=square root of (2K/m)
where K=(Ke energy exerted from own body)-(Kr resultant kinetic energy from opponent)
so, in order to increase the velocity V in which the opponent is being thrown out, one can either increase the kinetic energy K, or decrease the mass m of the opponent. Tai Chi works by both decreasing the "apparent" mass m of the opponent (of course, the "physical" mass of the opponent cannot be changed) and by neutralising the resultant kinetic energy Kr from the opponent.
Which means that, the better you are at reducing m and Kr, the less Ke you would need because as m approaches zero, V increases even though Ke, your own energy exerted could be very small! Hence, it is common to see an old master just lightly touching an opponent and the opponent flies off at 100km per hour! The saying in Tai Chi Classics "4 ounces to defeat 1000 pounds".
Basic Principles of REV
Although structures and techniques are important, unlike most Martial Arts and other Tai Chi styles, the Imperial Yang Family Tai Chi and the REV system do not rely on these alone and are not bound by them. While some Tai Chi schools will explain the generation of power by "pushing with the back foot" REV concentrates more on the mind and intention or "Yi", exactly as written by Wang Zhong Yue in the Tai Chi Classics.
For a simple example, in a static situation as the series of pictures above, Dr. Fung propelled instructor Quoc out with just two fingers. No matter how strong Dr. Fung may be it is not possible on brute force alone. How it was achieved was this: if the red line represents the force vector exerted by instructor Quoc, by manipulating at the point of contact, represented by the green curve, the force vector was reversed (hence the system is called Reverse Energy Vectors), neutralising instructor Quoc and propelling him outwards with minimal muscular effort. The higher the level, the more effective the reversal is and less energy would be needed. Effectively, at the higher levels all you need is a light touch and the opponent would be thrown off! You don't even need to have a good stance because none of the resultant forces will be exerted on to the rest of the body. Although for beginners, the physical alignment of the body structure is still important. Any part of the body could be used to throw off an opponent. Theoretically, one can emit power even when the feet are not touching the ground. The late Wang Yong Chuen could still bounce people two metres off the ground when he was wheel chair bound, one week before he passed away!
In a real life dynamic situation,
of course the force vector, the red line exerted by the opponent would be constantly
changing and re-adapting according to yourself. The principle still applies, but must be
coupled with the "Ting Wen Na Fang", which means Listen, Ask,
Lock, Release to effectively manipulate the force vectors, to "lock in" and
recognise when all the vectors are set up and ready to be released. As in the Tai Chi
Classic "when the enemy changes, I show my greatness". For more information on
Ting Wen Na Fang, go to 
Video
Lessons
The advantages of REV are:
To see REV in action visit the Demo Videos link and download some of the video
clips.